This invention relates to adhesive compositions. More particularly, this invention related to pressure-sensitive adhesive compositions suitable for use in the preparation of adhesive bandages, adhesive tapes, adhesive sheet materials and the like, which provide excellent adhesive characteristics when adhered to a part of the body and do not significantly lose said characteristics when immersed in or exposed to water.
This invention also relates to surgical sheet materials such as adhesive tapes and to adhesive bandages and dressings, such as coverings for cuts, abrasions and the like, which comprise a flexible backing member, one of whose major surfaces had adhered thereto a coating of the pressure-sensitive adhesives of the present invention.
Various types of pressure-sensitive adhesives have been proposed and utilized as the adhesive component in adhesive bandages, adhesive tapes and the like. Acrylate polymers, polyolefinic polymers and compounded systems based on natural or synthetic rubber polymers have all been tried or utilized as pressure-sensitive adhesives with varying degrees of success.
A pressure-sensitive adhesive must have certain characteristics to be useful. It must be sufficiently tacky, i.e., have sufficient "grab" or "quick-stick," to adhere quickly to the surface to which it is to be adhered. It must also continue to adhere to that surface over extended periods of time. A pressure-sensitive adhesive composition should also have sufficient internal strength to prevent splitting and leaving particles of adhesive on a surface to which an article coated with the adhesive has been adhered when the article is removed. Where the pressure-sensitive adhesive is designed for application to the skin, the problems of adherence are substantially increased. Although the initial tack or stick may be good, adherence over an extended period of time for many pressure-sensitive adhesives requires relatively high shear adhesion to withstand movement of the underlying skin. Also, the adhesive must be tailored to accommodate the nature of the underlying skin surface as where perspiration and other surface changes may occur. The problem is further complicated by the fact that any pressure-sensitive adhesive designed for application to the skin must release from the skin sufficiently readily to permit removal without skin damage. Where the adhesive is too strongly adhered to the skin and has substantial internal strength, small particles of the upper layer of skin are removed with the adhesive with resulting irritation to the skin. As a result, although many pressure-sensitive adhesives are available for various commercial uses, relatively few have been found which are suitable for articles for skin applications, particular in that many of those having desirable, high, sheer adhesion, have an undesirably high resistance to removal, or peel adhesion.
In order to reduce peel adhesion, the prior art incorporated waxes, fatty acids and silicones into pressure-sensitive compositions. Alternatively, the prior art reduced the tackifying resin to elastomer ratio to less than 1 to 2 in elastomeric pressure-sensitive adhesive formulations. However, these approaches have led to an undesirable reduction in holding or sheer power adhesion and in increased costs.